Float Liquid Level Switches

Float actuated devices for monitoring liquid level and activating switch contacts at predetermined liquid level thresholds.

A float liquid level switch is an instrument for monitoring the height of a liquid and tripping an electrical contact switch when a maximum, minimum or intermediate level has been reached. The liquid level switch output can then be utilised by other instrumentation to open a valve, illuminate a warning lamp, activate an audible alarm, or switch on a pump.

Featured liquid level measurement products

External Mounted Tank Level Sensors - External mounted level sensors for installing on the outside of a liquid storage tank to measure level of tank contents.
LMP307 Submersible Level Transmitter - Submersible level transmitter for measuring liquid level with a 4-20mA current loop or a 0-10V voltage output plus optional ATEX approval for intrinsically safe use in hazardous areas in ranges from 1mH2O up to 250mH2O. The LMP307 is suitable for use on potable water with no leaching, and can be supplied with a drinking water certificate according to DVGW and KTW.

Float liquid level switches are threshold contact trip devices which typically consist of a buoyancy component which is typically a sealed hollow ball or cylinder which will float on a liquid, and either a shaft assembly for vertical mounting, or a hinge mechanism for horizontal mounting.

As the level increases and decreases a float will be pushed up or drop down. The float can be connected to a hinge that opens and closes or slides along a shaft.

The position of the float along the shaft or the opening and closing of the hinge can be detected by various means.

A vertical mount sliding float type level switch will have a permanent magnet incorporated into the float which slides up and down the shaft. A magnetic reed switch is positioned along the shaft to the required level set point. When the float passes over the reed switch it will open or close the level switch circuit.

A horizontal mount hinged type float level switch will incorporate either a microswitch or a magnetic reed switch, which is activated by an actuator or lever connected to the float.

Featured liquid level measurement products

LMK458 Marine Approved Hydrostatic Level Transmitter - Marine approved level transmitter with 4-20mA output for measuring level of contents inside ship ballast, fuel, liquid cargo or wastewater tanks
Wash water break tank submersible level transducer with 1.6 m range and 4-20mA output - Monitor wash water levels in break tanks with this submersible 4-20mA transducer. Features high accuracy, 5m vented cable, and robust design.

It is possible to fit more than one switch to shaft type float switch, and provide liquid level control for a number of separate processes which are activated at different levels.

A float level switch makes direct contact with the liquid to be measured, and therefore material compatibility must be considered.

Since there are no pressure sensitive components exposed to the inside of the tank it is possible to fit float level switches to sealed pressurised tanks.

Float liquid level switches can be designed to mount through the top, side or bottom of a tank. Side entry type float level switches have hinged floats, and top and bottom entry type float level switches have sliding floats.

Featured liquid level measurement products

S12C SDI-12 Seawater Pressure & Temperature Transducer - SDI-12 protocol transducer for sensing water depth level and temperature in seawater, brackish water, tidal water, saline water or leachate.
Portable battery powered tank level gauge with submersible sensor - Is there anything portable that could be dropped into different sized and irregularly shaped tanks to measure the amount of change in liquid height?

Advantages

Different types available for top, side or bottom entry mounting
Cheapest type of liquid level switch
Simple design and construction
Not sensitive to changes in SG & density
Some types do not require power to operate
Surface disturbances such as ripples, foaming and bubbling will not affect performance
Dielectric constant or conductivity of fluid will not affect operation
Different materials for media compatibility can be specified
Vapours, condensation and mists will not affect operation
Vacuum and low pressure sealed tank will not compromise buoyancy of float

Disadvantages

Moving parts vulnerable to clogging, wear and tear, and damage
Fouling can cause unreliable movement or seizure of float actuation
Float actuation relies on liquid contact
Turbulence in the fluid may cause the float to move
Thick or sticky fluids may prevent the float from moving
Regular maintenance to ensure nothing is restricting float movement
Single point level switch with side entry type
Float assembly protruding into liquid causing obstruction, attracting fouling and hygienic cleanliness issues

Featured liquid level measurement products

LMK807 Plastic Submersible Level Transmitter - IP68 mid range pressure transmitter for measuring the level of highly contaminated and aggressive liquid media with a body made from PP-HT.
Marine aquaculture submersible seawater level & temperature transmitter - Use this dual output transmitter for monitor or controlling the water level and temperature of salt water ponds & tanks used in marine aquaculture systems.